Instrument for describing ellipses



April 1 1924.

w. JOHNSTON INSTRUMENT FOR DESCRIBING BLLIPSES Filed llay '1. 1923 2 Sheets-Sheet 1 INVENTOR.

i/Jbfi 72$ for A TTORNEY.

- IN V EN TOR.

'ATTO I W. JOHNSTGN INSTRUMENT FOR DESCRIBING ELLIPSES April 1 1924.

' Filed May 1923 2 Sheets-Sheet 2 Patented Again l, wi h eaten WILLIAM JOHNSTON, 0 BELFAST, IRELAND.

INSTRUMENT Application. filed To all whom it may concern:

Be it known that 1, WILLIAM JoHNs'roN, a subject of the King of England, residing at Bel'tast in the county of Antrim, Ireland have invented certain new and useful 1mproveuients in Instruments for Describing Ellipses, of which the following is a specification, reference being bad to the accompanying d awings.

This invention relates to drafting empleroents, and particularly to a rule or implement for describing elliptical figures.

The general object of? the invention is to provide an instrument of this character which. isextreinely convenient and suitable for designers, teachers and workmen and by which ellipses of any desired character within the range of the implement may be described without the necessity of laying): out points on the drawing sheet and then drawing the ellipse. v

'furtherobject is to provide an implement 0t this character having very few parts and these of a relatively simple na ture. whereby the instrument may be produced at a moderate cost.

it still turther object is to provide a device ct this character including a pointer fixed to one portion of the rule, a slide havin; sliding engagement with the rule and having a pointer, and a cord operatively connecting: the two pointers, the slide being so formed that it will be clamped automatically upon any portion of therule to which it may be set, and being further so formed that a mere depression of one portion of the slide will cause its clamping action upon the rule to be relieved to permit the easy movement of the slide along the rule toward or from the fixed pointer.

Another object is to provide means whereby one end of the cord may pass loosely through the pointer and through the rule and the slack ot' the cord taken up and the cord clamped in any adjusted posit-ion.

(lther objects have to do with the details of construction and arrangement of parts as will more fully hereinafter appear.

lily invention is illustrated in the accompanying drawings wherein Figure 1 is a perspective View of an instruroent for describing ellipses constructed in accordance with my invention and showing the instrument in actual use;

May 7, 1923.

F03 DE$CBIBINCT ELLIPSES.

Serial No. 637,221.

end of the rule. showing the cord clamping means thereon;

Figure l is a longitudinal sectional view of the slide;

Figure 5 a top plan view of the slide and a portion of the rule;

Figure 6 is a section on the line 66 of l igure 4i;

Figure 7 is a sectionon the line 77 of Figure l;

Figure 8 is a like View to Figure 7 but showing the toggle links depressed and the slide unclamped from the rule;

Figure 9 is a face view of the blank from which the slide is made.

Referring to these drawings, 10 design-ates a bar of any desired length as, for instance, approximately 23 and which bar constitutes a rule. This bar is preferably tapered from one edge face toward the other. The upper face 11 of the bar is provided with a series of inch graduations running from 1 to 20, these graduations being designated 12. The sides of the bar are formed with a series of longitudinal lines and transversely extending gra luations to form a series 13 of scales a, 7). (1., (Z. e 7' and 9', while the opposite face oi": the bar is formed with a series of longitudinal lines and these lines with graduations to provide a series of scales l3 correspondin rto the scales at to 9 but these scales being used for ellipses having different minor axes. The graduations 12 are used to set the slide to be hereafter described relative to the major axis of an ellipse to be described, while the scales a to g and the lit scales 13 on the opposite side of the bar or rule are designed to be used in setting the slide for the minor axis of the ellipse.

Attached to one end of the rule is a ferrule let of metal which snugly embraces the rule and is held thereto in any suitable manner, this ferrule being formed of metal and having; a downwardly extending hollow pointer 15. This pointer has a bore 16 which communicates with a bore 17 in the rule, which rule may be made of wood or any other suitable materiah this bore 17 being for the passage of a. cordwh'ich is held by a clamp mounted upon the upper face of the ferrule 14-. While I do not wish to be limited to any particular form of clamp, I have illustrated for this purpose the upper face of the ferrule as carrying a fixed clamping bar 18 held in place by a pair of screws and a movable clamping bar 19, this bar being angularly bent at its ends and these ends being slotted for the passage of screws 20. A cam 21 operates against the movable bar 19 and when the cam is turned with its handle longitudinally of the rule the jaw or clamping bar '19 will be moved toward the fixed jaw formed by the part 18. The cord 22 passes up through the bores 16 and 17 and then passes letween the clamping jaws and is held by these clamping jaws, as will hereafter more "fully appear. I do not wish to be limited to any particular design for the ferrule.

-Slidingly mounted upon. the rule is slide, designated generally 23. This s i.l fits the rule snugly and has downwardly extending pointer 2i which is hollow. 1 1o cord 22 is knotted inside of the pointer 24;, as at 25, and thus the cord is fixed to J extreme ape of the pointer and issues therefrom. The cord e tends over to the extreme apex of the po. cl. l5 and i is this cord 22 which is used i ellipse. The slide 23 so formed that it may be readily shifted by hand longitudinally of the bar or rule 10 and the upper face or" the slide 23 is formed with a pointer 26 enacting with the graduations l2 and each side of the slide is formed with seven pointers 27 designed to coact with the several sales 13. Thus, for instance, on one side (it the rule I have shown seven scales and there are seven pointers corresponding to these scales indicating the position of the slide on each of these scales.

The scales l3, esignated a. 7), 0, etc... are to indicate the minor axes oi ellipses to be described. In other words, it the major axis or the ellipse is 10 long while the ininor axis is 5, then the slide is moved until the pointer 26 coincides with the nun'ieral it) of the graduations l2 and then the cord is pulled taut and is held taut by means of the clamps l8 and 19 and then the slide 23 is shifted longitudinally along the rule until the pointer 27 having the numeral 10 thereon registers with the numeral 5 o! the scale a. Under those circumstances the cord when used as rea 1r (lest-i iced will cause a pencil orother marking instrument bean ing against the cord to describe an ellipse (see Figure 1).

I do not wish to be limited to the detailed construction of the slide as illustrated as this might be varied in many ways without departing from the spirit otthe invention, but as illustrated the slide is formed of a single blank of metal, as shown in Figure 9. This blank is formed to pr0- ride the two side walls 28, these side walls l 5' coni'iected by an approximately triangular portion which, when the blank is toided, forms the pointer This triangular portion of the blank is to be folded on the dotted lines illustrated in Figure 9, the small tiap 29 forming the inside wall of the pointer, that is that wall facing away from the pointer 15.

The marf-ns oi each wing 28 which intersect the triangular portion 2iare cut to form a series of triangles or interdieitated portions so tl it when the blank is folded these inter-d tated portions on one wing it into the like portions on the other wing and form when so folded and brazed, the under face of the slide. These triangular portions 30 each has an aperture at its base and a tongue or strip 31 is formed in the blank between the confronting ends of the blank, that is between those ends which form the pointers 27, which tongue or strip is bent on the line 00 and extends along the bottom of the slide just above and is brazed to the interdigitated 7 portions and this tongue 31 is formed with laterally projecting tabs or studs which engage in the perforations in the triangles 30. This strip Ell is also formed with a relatively large opening ti'or threading the fixed or knot ted end of the cord 22. O1"- course, it will understood that when the blank is folded the triangular teeth 30 of the two wings fit into each other and are solder d together and that the strip or tongue is told-ed down inside of these triangles 30 with the studs 3. extending through the bases or the triangles and also soldered in place, thus forming the foot or bottom of the slide. The margin of each wing opposite to the iuterdigitated portions is cut, as shown in Figure 9, to provide at the middle of each portion the spaced hinge heads 3% and the flanges 33 which are designed to be turned inward approxirnately at right angles to the sides or wings 28, the extremity o'l these flanges being bent upward, as at 36, for: iug lugs adapted to be e gaged by circular springs 37, the upwardly turned flanges being notched, as at 38, to interlock with the springs so that the springs cannot shift longitudinally.

It will be noted from l igure ethat each wing or side of the blank 28 is slotted at two points. as at 39, the slots extending parallel to the ends ot the sides and nearly to the interdigitated portions. The free ends of the parts 40 defined by said slot are angularly bent so that the angularly bent portions ll of one wing or side 28 overlaps the angular-1y bent portions ll. of the other side or wing. Thus while the end portions of each side or wing 28 of the slide are held from any compressive or expansive move mentand held to fit snugly and move smoothly upon the rule 1 the middle portion of the slide formed by the opposite walls or wings free to be forced in ward or -:-:pan(;le l outward. These sides 25% are forced inward into clamping engagement with the rule lit by means of the springs 37, and for the purpose of forcing these sides 28 outward to relieve the clamping action upon the rule I provide the toggle links 4-2 device apart against the action of the spring 3'7 and thus relieve the clamping action of the slide on the rule.

l Vhile T have found that this particular manner of constructing the slide is very effective and permits the slide to be made in one piece of material, I do not wish to be limited thereto, as other means might be used for causing the slide to snugly embrace the rule 10 and clamping the slide in any adjusted position. Furthermore, it is obvious that this clamp might be modified in many ways without departing from the spirit of the invention as defined in the appended claims.

The principle involved with this drawing instrument is that a definite length of any ellipse can be secured by using exactly the same length of cord, no matter to what minor axis the cord may be afterwards adjusted.

In the use of this device, the slide 23 is adjusted along the rule until the pointer 26 is in exact accordance with the length as indicated by thegraduations 12 of the ellipse to be described, that is is exactly equal to the major axis of the ellipse to be described. The cord is then pulled taut and held in this taut condition by means of theclamp formed of the inen'ibers 18 and 19 operated by the cam 21. The slide 23 is then again adjusted along the rule in accordance with the minor axis of the ellipse to be described, that is in accordance with the graduations i3 indicating minor axes. This adjustment is secured by using the pointer 27 which is opposite to the series of figures on the side of the slot. which give the major axis of the ellipse. Thus. for instance, if the major axis is 8 the scale 0 is to be used. If it is 6 th scale 6 is used, etc. The slide is then moved along until the corresponding pointer reaches that graduation on the selected scale 18 which corresponds to the distance be tween the foci of the ellipse.

For the actual drawing of the ellipse, the rule is placed when adjusted on the surface to be drawn, the rule being disposed on one side and because of the fact that the rule is tapered in cross section the two pointers 15 and 24: will have their apiccs resting directly on the surface. The rule is then held firmly on the surface on which the ellipse .is to be described and the pencil is placed in an obvious manner within the cord, the core is drawn out to one end of the major ax s. the the pencil is moved within the limits defined by the cord, and this half of th ellipse will be described. When half of the ellipse has been described the rule is simply turned over on its two points and the operation repeated, which will describe the eruiire ellipse and describe it accurately.

lit will be seen that the slide may be readily manipulated by pressing downward onthe toggle links, which releases the grip of the springs, and then the entire slide can be easily slid along the rule to any desired position. The removal of the thumb pressure against the toggle links permits the springs 37 to cause the slide to grip the rule and hold the slide firmly in its adjusted position.

I have illustrated the graduations on the scales L3 as being inch, half inch, and quarter graduations, but it will be understood that liner groups might be used. Any ellipse not over 18 long, assuming that the rule is 20", that may not be fully worked out on the scales 13 can be obtained by adjusting for the exact length desired and then pushback slide 23 until the slack of the cord extends to half the width desired.

It will be seen that the instrument which" I have described has its elements reduced to a minimum and that none of them are of a complicated nature. The complete instrument can be produced at a moderate cost without being in any way inaccurate or in eiiicient. The ferrule and the slide can be readily produced either in single stampings or partly stamped with solid or hollow brazed-on pointers 15 and 24. With a rule of this character there is one member to be adjusted, namely the slide 23, there are no screws to tighten or'to slacken, the slide is instantly adjustable and yet will retain its place firmly, and the triangular section of tie rule permits the operating cord to lie flat on thesurface of the face being drawn on, thus making for perfect work. No setting out of any measurements on the paper or other surface being drawn on is required. The system of scaling the figures of measurements on the rule itself, those for the major axes on the back of the rule and those for minor axes on the two sides, aids very con siderably in permitting quick adjustment of the device. It will be obvious that the rule may be of any dimensions suitable for the work to be performmil. Thus in certain circumstances very long rules will have to be till used and in others relatively small rules, but normally the rules will be in two sizes, one operating for ellipses of from 2 to 12" in length and the other operating for ellipses from 9 to 30 or 86".

I claim z- I 1. An instrument for describing ellipses comprising a rule having converging side edges, a hollow pointer fixed to the rule, a slide mounted on the rule and having a hollow pointer, the apices of the pointers being disposed at the intersections of planes forming a continuation of the converging side faces of the rule, a cord attached to the apex of one pointer, the cord extending loosely through the apex of the other pointer, and means associated with the last named pointer for clamping the cord.

2. An instrument for describing ellipses comprising a rule having a fixed hollow pointer on one end, a slide shiftable along the rule and having a hollow pointer, a cord extending through the apex of the last named pointer and extending loosely through the apex of the other pointer, means in connection with the first named pointer for clamping the cord in place, the rule having graduations upon one face thereof corresponding in length to the major axes of the ellipses to be described and having on one side a series of scales, each scale being associated with a definite length of major axis, each scale being graduated to indicate the length of the mlnor axis of the ellipse whose major axis is associated with the scale, the slide being formed with a plurality of pointers coacting with the several scales.

3. An instrument for describing ellipses comprising a rule having converging side faces, a ferrule mounted upon one end of the rule and having a hollow pointer, a slide mounted upon the rule and having means whereby it may be clamped in adjusted positions thereon and the slide having a hollow pointer, a cord attached within the last named hollow pointer and extending out through the apex thereof and extending through the apex of the pointer on the ferrule, the slack of the cord being adapted to be drawn up through the last named hollow pointer to tighten the cord, means on the ferrule for clamping the cord and holding it tightened, one face of the rule being provided with a graduation corresponding to various major diameters of ellipses and another face of the rule being provided with a series of scales, each graduated to correspond with a plurality of minor axes, each scale being associated with an ellipse of a major diameter and the slide being formed with pointers coacting with said several scales.

4. An instrument for describing ellipses comprising a rule, a ferrule mounted upon one end of the rule and having a hollow pointer, a slide mounted upon the rule for movement toward or from the ferrule and having a hollow pointer, a cord attached within the last named hollow pointer x tending through the apex thereof, extending to and through the apex of the other pointer, the free end of the cord passing to the exterior of the ferrule, a cord clamp on the ferrule, the slide being formed to provide two opposed sides engaging against the sides of the rule, springs urging said sides into clamping engagement with the rule, and manually operable means mounted on the slide whereby the sides of the slide may be forced away from the rule to permit the sliding of the slide on the rule, the rule being provided with a scale formed with a series of graduations indicating different major diameters of ellipses and with a series of scales each associated with a particular major diameter, each of the last named scales being graduated in accordance with a plurality of minor diameters, the slide being formed with pointers coacting with the several scales.

5. In a rule, a slide thereon coacting with graduations on the rule, the slide having opposite sides connected along one edge, the opposite edges being separated, a spring engaging the last named edges to urge the sides toward each other and against the rule, and means for forcing the separated edges of the sides apart against the action of the spring comprising two a-ngularly related members each hinged to one of the sides, the members being hinged to each other.

6. In a rule, a slide thereon coacting with graduations on the rule, the slide having opposite sides connected along one edge, the opposite edges being separated, a spring engaging the last named edges to urge the sides toward each other and against the rule, and means for forcing the separated edges of the sides apart against the action of the spring comprising two angularly related members each hinged to one of the sides, the members being hinged to each other.

7. A rule, a slide thereon coacting with gl'aduations on the rule, the slide having opposite side walls operatively connected along one edge, the opposite edges being separated and formed to provide hinge beads and in wardly extending flanges having angularly bent margins, circular split springs engaging said flanges and urging the two side walls against the rule, and toggle links hinged to each other and diverging toward the side walls and operatively hinged to the hinge beads thereof.

8. A rule, a slide thereon coacting with graduations on the rule and having opposite side walls connected along one edge by a web and at its opposite edges being sep arated for a distance inward of each end,

each end of the side well being separated from the body thereof by a slot extending through each side Wall, the end portions of the side Well being joined, springs urging 1 the middle portions of the side walls toward each other and against the rule, and a pair of toggle links operatively hinged to each other andhinged to the side Walls whereby the side walls may be separated against the force of the springs.

In testimony whereof I hereunto atiix my signature.

WILLIAM JOHNSTON. 

